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<div class="titlepage"><div><div><h3 class="title">
<a name="boost_typetraits.reference.alignment_of"></a><a class="link" href="alignment_of.html" title="alignment_of">alignment_of</a>
</h3></div></div></div>
<pre class="programlisting"><span class="keyword">template</span> <span class="special">&lt;</span><span class="keyword">class</span> <span class="identifier">T</span><span class="special">&gt;</span>
<span class="keyword">struct</span> <span class="identifier">alignment_of</span> <span class="special">:</span> <span class="keyword">public</span> <a class="link" href="integral_constant.html" title="integral_constant">integral_constant</a><span class="special">&lt;</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">size_t</span><span class="special">,</span> <span class="identifier">ALIGNOF</span><span class="special">(</span><span class="identifier">T</span><span class="special">)&gt;</span> <span class="special">{};</span>
</pre>
<p>
        <span class="bold"><strong>Inherits:</strong></span> Class template <code class="computeroutput"><span class="identifier">alignment_of</span></code>
        inherits from <code class="computeroutput"><a class="link" href="integral_constant.html" title="integral_constant">integral_constant</a><span class="special">&lt;</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">size_t</span><span class="special">,</span> <span class="identifier">ALIGNOF</span><span class="special">(</span><span class="identifier">T</span><span class="special">)&gt;</span></code>,
        where <code class="computeroutput"><span class="identifier">ALIGNOF</span><span class="special">(</span><span class="identifier">T</span><span class="special">)</span></code> is the
        alignment of type T.
      </p>
<p>
        <span class="emphasis"><em>Note: strictly speaking you should only rely on the value of <code class="computeroutput"><span class="identifier">ALIGNOF</span><span class="special">(</span><span class="identifier">T</span><span class="special">)</span></code> being
        a multiple of the true alignment of T, although in practice it does compute
        the correct value in all the cases we know about.</em></span>
      </p>
<p>
        <span class="bold"><strong>Header:</strong></span> <code class="computeroutput"> <span class="preprocessor">#include</span>
        <span class="special">&lt;</span><span class="identifier">boost</span><span class="special">/</span><span class="identifier">type_traits</span><span class="special">/</span><span class="identifier">alignment_of</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">&gt;</span></code>
        or <code class="computeroutput"> <span class="preprocessor">#include</span> <span class="special">&lt;</span><span class="identifier">boost</span><span class="special">/</span><span class="identifier">type_traits</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">&gt;</span></code>
      </p>
<p>
        <span class="bold"><strong>Examples:</strong></span>
      </p>
<div class="blockquote"><blockquote class="blockquote"><p>
          <code class="computeroutput"><span class="identifier">alignment_of</span><span class="special">&lt;</span><span class="keyword">int</span><span class="special">&gt;</span></code>
          inherits from <code class="computeroutput"><a class="link" href="integral_constant.html" title="integral_constant">integral_constant</a><span class="special">&lt;</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">size_t</span><span class="special">,</span> <span class="identifier">ALIGNOF</span><span class="special">(</span><span class="keyword">int</span><span class="special">)&gt;</span></code>.
        </p></blockquote></div>
<div class="blockquote"><blockquote class="blockquote"><p>
          <code class="computeroutput"><span class="identifier">alignment_of</span><span class="special">&lt;</span><span class="keyword">char</span><span class="special">&gt;::</span><span class="identifier">type</span></code> is the type <code class="computeroutput"><a class="link" href="integral_constant.html" title="integral_constant">integral_constant</a><span class="special">&lt;</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">size_t</span><span class="special">,</span> <span class="identifier">ALIGNOF</span><span class="special">(</span><span class="keyword">char</span><span class="special">)&gt;</span></code>.
        </p></blockquote></div>
<div class="blockquote"><blockquote class="blockquote"><p>
          <code class="computeroutput"><span class="identifier">alignment_of</span><span class="special">&lt;</span><span class="keyword">double</span><span class="special">&gt;::</span><span class="identifier">value</span></code> is an integral constant expression
          with value <code class="computeroutput"><span class="identifier">ALIGNOF</span><span class="special">(</span><span class="keyword">double</span><span class="special">)</span></code>.
        </p></blockquote></div>
<div class="blockquote"><blockquote class="blockquote"><p>
          <code class="computeroutput"><span class="identifier">alignment_of</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&gt;::</span><span class="identifier">value_type</span></code> is the type <code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">size_t</span></code>.
        </p></blockquote></div>
<div class="important"><table border="0" summary="Important">
<tr>
<td rowspan="2" align="center" valign="top" width="25"><img alt="[Important]" src="../../../../../../doc/src/images/important.png"></td>
<th align="left">Important</th>
</tr>
<tr><td align="left" valign="top">
<p>
          Visual C++ users should note that MSVC has varying definitions of "alignment".
          For example consider the following code:
        </p>
<p>
</p>
<pre class="programlisting"><span class="keyword">typedef</span> <span class="keyword">long</span> <span class="keyword">long</span> <span class="identifier">align_t</span><span class="special">;</span>
<span class="identifier">assert</span><span class="special">(</span><span class="identifier">boost</span><span class="special">::</span><span class="identifier">alignment_of</span><span class="special">&lt;</span><span class="identifier">align_t</span><span class="special">&gt;::</span><span class="identifier">value</span> <span class="special">%</span> <span class="number">8</span> <span class="special">==</span> <span class="number">0</span><span class="special">);</span>
<span class="identifier">align_t</span> <span class="identifier">a</span><span class="special">;</span>
<span class="identifier">assert</span><span class="special">(((</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">uintptr_t</span><span class="special">)&amp;</span><span class="identifier">a</span> <span class="special">%</span> <span class="number">8</span><span class="special">)</span> <span class="special">==</span> <span class="number">0</span><span class="special">);</span>
<span class="keyword">char</span> <span class="identifier">c</span> <span class="special">=</span> <span class="number">0</span><span class="special">;</span>
<span class="identifier">align_t</span> <span class="identifier">a1</span><span class="special">;</span>
<span class="identifier">assert</span><span class="special">(((</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">uintptr_t</span><span class="special">)&amp;</span><span class="identifier">a1</span> <span class="special">%</span> <span class="number">8</span><span class="special">)</span> <span class="special">==</span> <span class="number">0</span><span class="special">);</span>
</pre>
<p>
        </p>
<p>
          In this code, even though <code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">alignment_of</span><span class="special">&lt;</span><span class="identifier">align_t</span><span class="special">&gt;</span></code> reports that <code class="computeroutput"><span class="identifier">align_t</span></code>
          has 8-byte alignment, the final assert will fail for a 32-bit build because
          <code class="computeroutput"><span class="identifier">a1</span></code> is not aligned on an
          8 byte boundary. Note that had we used the MSVC intrinsic <code class="computeroutput"><span class="identifier">__alignof</span></code> in place of <code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">alignment_of</span></code>
          we would still get the same result. In fact for MSVC alignment requirements
          (and promises) only really apply to dynamic storage, and not the stack.
        </p>
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      Frederic Bron, Steve Cleary, Beman Dawes, Glen Fernandes, Aleksey Gurtovoy,
      Howard Hinnant, Jesse Jones, Mat Marcus, Itay Maman, John Maddock, Alexander
      Nasonov, Thorsten Ottosen, Roman Perepelitsa, Robert Ramey, Jeremy Siek, Robert
      Stewart and Steven Watanabe<p>
        Distributed under the Boost Software License, Version 1.0. (See accompanying
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